Brush cutters are well known as a kind of powered work machines. These brush cutters include typically a two-stroke air-cooled engine of which the output is transmitted to a cutting blade through a power transmission member provided in a long operation rod. The blade is thus rotated axially to cut grass and bushes.
As disclosed in Japanese Patent Laid-Open Publication No. H 9(1997)-303354 (Patent Document 1), the operation rod is detachably connected to a housing (cover member) of the power source. More specifically, the engine power is outputted through a centrifugal clutch. The operation rod is detachably connected to the housing that encloses the centrifugal clutch. In this mechanism of connection, the housing has a cylindrical fixing portion projecting and opening forward. The operation rod is inserted and fixed with its rear end in a pipe-shaped fixture fixed to the cylindrical fixing portion, whereby the operation rod is fixed to the housing. Of course, when the operation rod is fixed to the cylinder, the power transmission member, i.e. a rotating shaft, provided in the operation rod is mechanically connected to an output shaft of the centrifugal clutch.
The retaining rib formed at a lengthwise intermediate position of a fixture body of a connecting structure disclosed in Patent Document 1 is shown in FIG. 8. In this illustration, reference numeral 1 denotes a housing, and reference numeral 2 denotes a sheath of an operation rod, in which a power transmission member extends. As shown, a rubber cushion 3 is interposed between the sheath 2 and housing 1. The rubber cushion 3 forms a part of a pipe-shaped fixture 4.
As shown, the pipe-shaped fixture 4 includes a cylindrical main body 5 of the pipe-shaped fixture 4 (hereafter called fixture body 5). By tightening bolt-and-nut engagement using a bolt hole 6 formed at the front end portion of the fixture body 5, the pipe-shaped fixture 4 can be reduced in diameter to secure the operation rod 2 at the rear end thereof. The rubber cushion 3 is firmly fixed to the fixture body 5. Specifically, the rubber cushion 3 is formed by putting the fixture body 5 into a forming die and filling the forming die with melted rubber.
FIGS. 9 and 10 show the fixture body 5 and rubber cushion 3 used in the conventional pipe-shaped fixture 4. As shown, the rubber cushion 3 is formed on the fixture body 5 except the front end portion of the latter and has a size large enough to cover the rear end face of the fixture body 5. Also seen in FIGS. 8 to 10, a circumferential retaining rib 7 is formed at a lengthwise intermediate position of the fixture body 5.
Referring back to FIG. 8, the housing 1 includes a cylindrical fixing portion 8 projecting and opening forward. The pipe-shaped fixture 4 is inserted into the cylindrical fixing portion 8. The cylindrical fixing portion 8 has an inner circumference tapered rearward, namely, toward its deep end, and the rubber cushion 3 of the pipe-shaped fixture 4 has an outer circumference tapered complementarily to the inner circumference of the cylindrical fixing portion 8. When the pipe-shaped fixture 4 is inserted into the cylindrical fixing portion 8, the outer circumference of the rubber cushion 3 gets in close contact with the inner circumference of the cylindrical fixing portion 8.
As shown in FIG. 8, the cylindrical fixing portion 8 has a circumferential groove 9 formed in the inner circumference near its front end. By inserting the pipe-shaped fixture 4 into the cylindrical fixing portion 8 of the housing 1 and then installing a snap ring 10 in the circumferential groove 9, the pipe-shaped fixture 4 is fixed to the cylindrical fixing portion 8 and restrained by the snap ring 10 not to disengage from the cylindrical fixing portion 8.
By interposing the rubber cushion 3 between the operation rod 2 and housing 1, vibration of an engine (not shown) can be limited from being transmitted to the sheath of the operation rod 2, which encloses the power transmission member, and vibration of the operation rod 2 can be limited from being transmitted to the housing 1.